The invention relates to an implantable pump for drug infusion and more particularly to a pump having a remotely activatable valve for triggering drug release.
Implantable infusion pumps allow the directed delivery of pharmacological agents to discrete locations within an animal either as a discrete dose or as a constant infusion.
Currently available technology does not permit acute bolus infusion of pharmacologic agents in conscious, behaving, non-tethered, small animals. This is a handicap for the fields of pharmacology, animal behavior, physiology, and imaging in that rats and mice are the most widely used and cost-effective animal models. Small, implantable slow-release osmotic pumps are commercially available and are widely used by researchers across numerous disciplines. Slow-release pumps, however, allow only examination of chronic drug effects. Acute bolus injection only is possible in restrained, immobilized or tethered animals. For many applications, however, the physical aspects of immobilization or the stress of needle sticks themselves changes the animal""s behavior, physiology or pharmacologic response, leaving the physiologic significance of any results up to interpretation.
It is well known that the presence or absence of stress may substantially change an animal""s behavior. Even minor routine handling procedures can induce a marked stress in animals, although the animal has been trained to this procedure and looks quiet. Handling an animal or drug injection by needle will largely suppress behaviors such as aggression, sleep, and mating at the time of occurrence. This has made it difficult to study the neurochemical basis of behaviors which otherwise might be characterized using acute administration of pharmacologic agents. Examination of the acute pharmacologic effects on a behavior at the time of its occurrence has been tried in tethered animals connected via a head cap or body port to an external catheter that is supported by a swivel joint and balance arm. Such techniques are practical only in the study of behaviors of animals in isolation and are limited to a subset of behaviors which present a low risk of entanglement of the animal with its cable. The extent to which the stress of tethering reshapes xe2x80x98normalxe2x80x99 behavior in these paradigms is likely substantial.
In the field of neurobehavioral pharmacology, there is a critical need for a means of acutely administering pharmacologic agents in a nonstressful manner.
Although implantable infusion pumps are known, none meet this need. For example, a compact spring-activated pump has been disclosed (Wigness, B. D., Dorman, F. D., Rohde, T. D. and Buchwald, H. The spring-driven implantable pump. A low-cost alternative, Asaio Journal, 38 (1992) M454-457; Dorman and Buchwald, U.S. Pat. No. 4,772,263). This pump does not address the need for a remotely-activated infusion pump capable of bolus infusions. Likewise, Ashton et al. (U.S. Pat. No. 5,836,935) disclose an implantable infusion pump for the controlled release of a drug, but does not recognize the need for remote activation or a control valve.
There exists a need for an implantable infusion pump capable of infusing a bolus of drug that can be remotely operated, is compact and can be readily manufactured.
The invention provides a pump for drug delivery having a reservoir with an elastically deformable member, wherein the reservoir is in fluid communication with an outlet catheter, having an electrically activated valve in fluid communication with the reservoir, and having a control system containing a sensor such that the valve can be remotely operated. The sensor can be sensitive to a magnetic field or any electromagnetic radiation including, for example, infrared light. In one embodiment, the pump is compact and can be manufactured at a low cost.
In a preferred embodiment, the valve is closed in its resting state such that upon activation of the control system, the pump can provide a bolus injection of an infusate. In a preferred embodiment, the valve is a solenoid valve.
The entire pump can be implanted in an organism subcutaneously or a portion of the pump can be mounted percutaneously. In one embodiment, the entire pump can be implanted in an animal. In another embodiment, the reservoir and drug delivery channel can be implanted subcutaneously, while the sensor is attached percutaneously.
The pump can be of such a size that it can be implanted into a small mammal, for example a rodent. In various embodiments, the pump has a reservoir with a volume of between about 0.1 milliliters (ml) and about 10 ml, preferably between about 0.1 ml and about 5 ml, and even more preferably between about 0.1 ml and about 2 ml.
In one embodiment, the elastically deformable member of the reservoir acts as a septum and can reseal after puncture by a hypodermic needle. The reservoir also can contain an refilling injection port. In one embodiment, the refilling injection port is a septum that reseals after puncture by a hypodermic needle. The refilling injection port also can be tubing in fluid communication with the reservoir with a septum that reseals after puncture by a hypodermic needle.
The pump also can contain an ejection chamber in fluid communication with the valve and the outlet catheter. In one embodiment, the ejection chamber is a coil of tubing.